[DRAFT] Support FIPS build w/ CPU Jitter

[justsmth]

Issues:

Addresses: CryptoAlg-2814

Description of changes:

• Detects environment variable AWS_LC_FIPS_SYS_CPU_JITTER_ENTROPY indicating that AWS-LC should be built to use cpu jitter entropy.
• Adds functions to allow consumers to verify cpu jitter entropy is in use at runtime.

Call-outs:

• The required FIPS_is_entropy_cpu_jitter function is not yet available on the FIPS branch. So the check currently only verifies that the "cpu_jitter_entropy" configuration was successfully detected by the build scripts.
• This PR depends on: Pregen bindings for aarch64-linux-android; Prepare aws-lc-sys v0.25.0 #649

Testing:

• Added script/CI that verifies that the fips_cpu_jitter_entropy() assertion succeeds.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.